A snare drum is structured as follows: a top-side drumhead and a bottom-side drumhead are disposed to close both ends of a shell body, having hoops interposed therebetween, respectively. Further, a plurality of head adjustment devices for adjusting tension of the drumheads is disposed at an equal angular interval, so as to connect the top-side hoop and the bottom-side hoop. Strainers located in opposition at positions differing 180° at the shell body hold a snare assembly made up of a plurality of snare wires such that the snare assembly can be switched between a contact/noncontact state with respect to the bottom-side drumhead (for example, see Patent Documents 1 to 3). At least one of the pair of strainers is a strainer equipped with a switch mechanism that allows the snare assembly to switch between the contact/noncontact states by moving up and down the end of the snare assembly being held. The other may also be a similar strainer equipped with a switch mechanism, or it may be a fixed type strainer without such a switch mechanism.
What has conventionally been provided as such a strainer equipped with a switch mechanism is a strainer structured with components such as: a base element fixed at the exterior circumferential surface of a shell body; a snare assembly holding element mounted on the base element so as to be freely movable upward and downward; a switch mechanism that moves forward and backward the snare assembly holding element relative to the base element so as to bring the movable end of the snare assembly into contact or out of contact with a bottom-side drumhead; and a tension adjustment screw that similarly moves forward and backward the snare assembly holding element relative to the base element so as to fine-tune the tension of the snare assembly (for example, see Patent Documents 1 and 2).
In particular, as to such a switch mechanism that moves the snare assembly holding element to switch the snare assembly between the contact/noncontact states, Patent Document 1 proposes a mechanism as a cam mechanism, in which rotation of a switch lever moves a circular cam, and a slide plate goes down with a snare assembly holding element through a cam aperture; and reverse rotation of the switch lever lifts up the slide plate with the snare assembly holding element through the circular cam and the cam aperture. However, such a cam mechanism is prone to suffer from backlash due to wear and the like caused by a concentrated load acting upon a portion around the cam aperture. Such backlash causes a reduction in operation feel. Further, the positional attitude of the cam mechanism in its contact/noncontact states is unstable because of its mechanism, and the movement allowance of the switch lever in its up (contact) state is small. Thus, just a small amount of movement of the lever easily allows a noncontact state to be entered.
Patent Document 2 proposes a mechanism in which a linkage mechanism is employed as the switch mechanism. When a switch is operated upward, a link connected to the rotating switch moves in a direction to push up the shaft of a snare assembly holding element connected to the top end thereof, whereby the snare assembly is caused to enter a contact state indirectly through a slide member. However, the linkage mechanism is configured to push up the link connected to the lever so as to move the snare assembly holding element upward. Therefore, force in diagonal direction acting upon the snare assembly holding element from the shaft at the beginning of push-up is great. Hence, similarly to the above-described cam mechanism, it is prone to suffer from backlash which causes a reduction in operation feel. Furthermore, again, because the force acts in the diagonal direction at the beginning of push-up, the force required for the operation is great, putting a burden upon the player.
Another proposed mechanism is as follows: instead of moving the snare assembly holding element up and down, a stretching rod is provided to a lever member. When a switch lever is rotated clockwise by a prescribed angle, the stretching rod goes down to approach the shell body, whereby a snare assembly connection member is released from a tension state and brought into contact with the rear end of the slope of an arm member. As a result, the snare assembly is released from the tension state and sags under its own weight (see Patent Document 3). However, such a mechanism poses problems of a very complicated structure and an increased burden on the snare assembly string because of the stretching rod directly abutting on the snare assembly string.
Further, as shown in FIG. 17 (a), such snare assembly end holding structures with a strainer equipped with a switch mechanism or with a fixed type strainer are each conventionally been structured as follows: a stopper plate 76 is mounted on a snare assembly stopper face 30 of a strainer 1 with a bolt 77, and the bolt 77 is tightened in a state where a snare assembly end 105 is passed through between the snare assembly stopper face 30 and the stopper plate 76, whereby the snare assembly end 105 is clamped therebetween. With such a structure, the axial force obtained by tightening the bolt 77 acts upon the snare assembly end 105 as the clamping force. Accordingly, when the bolt tightening force is weak, the snare assembly end 105 is easily loosened, to adversely affect the musical performance. Therefore, as shown in FIG. 17 (b), measures have conventionally been taken to prevent loosening by two pieces of stopper plates 76, such that the snare assembly end 105 having passed through between one of the stopper plates 76 and the stopper face 30 is again passed through between the stopper plates 76, thereby doubling the length of the snare assembly end being clamped. However, such a holding structure involves complicated attaching work of the snare assembly end to the stopper plates, and invites an increase in both costs and total weight because of the increased number of the stopper plate.
A possible structure for preventing loosening with one stopper plate may be to provide a projection or the like at the interior surface of the stopper plate such that the projection meshes with the snare assembly end (for example, see Patent Document 1). However, with such a structure, the clamping force is concentrated to the projection portion, putting a load on a part of the snare assembly end. Therefore, repeated use (in particular, repeated switching operation between contact/noncontact) may break the snare assembly end. Further, with such a single-point concentration type holding structure, the snare assembly end easily break with the slightest excessive bolt tightening force. Hence, the adjustment thereof becomes very delicate work, which gives the player cause for anxiety.    Patent Document 1: JP-A No. 7-39093    Patent Document 2: JP-A No. 2005-331922    Patent Document 3: JP-A No. 2005-227660